Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$92.71	7.182%	$99.3684	$99.37	$99.35	$99.40
Purchase #2	$37.39	10.263%	$41.2273	$41.23	$41.25	$41.20
Purchase #3	$144.74	7.512%	$155.6129	$155.61	$155.60	$155.60
Purchase #4	$208.71	6.679%	$222.6497	$222.65	$222.65	$222.60
Purchase #5	$147.48	5.400%	$155.4439	$155.44	$155.45	$155.40
Purchase #6	$174.53	5.739%	$184.5463	$184.55	$184.55	$184.50
Purchase #7	$32.66	11.825%	$36.522	$36.52	$36.50	$36.50
7 purchase totals =	$838.22		$895.3705	$895.37	$895.35	$895.20